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Method for detecting retained austenite and under-tempering by using Rockwell and Leeb hardness contrast method

A technology of retained austenite and Leeb hardness, applied in the field of steel heat treatment quality inspection, can solve the problems of workpiece cracking, insufficient tempering damage, cracking and other problems

Active Publication Date: 2007-07-11
DONGFENG MOTOR CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Insufficient tempering is very dangerous
It will cause the workpiece to crack during grinding and wire cutting; it will crack during use

Method used

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  • Method for detecting retained austenite and under-tempering by using Rockwell and Leeb hardness contrast method
  • Method for detecting retained austenite and under-tempering by using Rockwell and Leeb hardness contrast method
  • Method for detecting retained austenite and under-tempering by using Rockwell and Leeb hardness contrast method

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0065] Embodiment 1, the first phenomenon:

[0066] The hardness value of the workpiece detected by the Rockwell hardness tester is 61.5HRC; the hardness value of the workpiece measured by the Leeb hardness tester is converted to Rockwell 59.9-61.2HRCLD (all the following Leeb hardness values ​​are directly converted into Rockwell values ​​by the instrument). The hardness value of each part of the workpiece is relatively uniform regardless of whether it is detected by a Leeb hardness tester or a Rockwell hardness tester. The metallographic structure is martensite + block granular carbide + a small amount of retained austenite, and the structure is fully tempered. See Figures 13 and 14.

[0067] Corrosion conditions: 4% nitric alcohol at room temperature 25°C for two minutes.

Embodiment 2

[0068] Embodiment 2, the second phenomenon:

[0069] The hardness value of the workpiece detected by the Rockwell hardness tester is 58-60HRC; the hardness value of the workpiece measured by the Leeb hardness tester is 48-55HRCLD. The value measured by the Leeb hardness tester at the periphery of the workpiece is 52-55HRCLD, and the value measured by the Leeb hardness tester near the middle is 48-51HRCLD; the hardness value deviation of each part of the workpiece measured by the Rockwell hardness tester is only 1-2HRC. The metallographic structure is martensite + massive granular carbide + a large amount of retained austenite, and the organization is insufficiently tempered. See Figures 15 and 16.

[0070] Corrosion conditions: 4% nitric alcohol at room temperature 25°C for two minutes.

Embodiment 3

[0071] Embodiment 3, the third phenomenon:

[0072] The hardness value of the workpiece measured by the Rockwell hardness tester is 51-52HRC; the hardness value of the workpiece measured by the Leeb hardness tester is 50-53HRCLD. The hardness values ​​of each part of the workpiece measured by the two hardness testers are relatively uniform. The metallographic structure is cryptocrystalline martensite + massive granular carbide + a small amount of retained austenite, and the structure is fully tempered. See Figure 17 and Figure 18.

[0073] Corrosion conditions: 4% nitric alcohol at room temperature 25°C for two minutes.

[0074] From the above data and metallographic structure, it can be concluded that: the first phenomenon, the workpiece hardness is qualified, and the metallographic structure is normal, which can determine the quality is qualified; the second phenomenon, the difference between the two hardness tester results of the workpiece is greater than or equal to 3HRC...

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Abstract

The invention uses Rockwell and Brinell hardness tester to inspect each hardness value after heat treatment tempering, with bigger difference of the values, more residue of austenite inside the working piece. The insufficient tempering standard is when the Rockwell and Brinell hardness value difference bigger or equal to 3HRC, otherwise, the qualified tempering. It is quick, simple, and convenient with on site inspection for each part together with high accuracy and free from pollution. It not only applies to Cr12MoV steel tempering insufficiency inspection of quenching status, also applies to secondary hardening of high alloy steel tempering insufficiency.

Description

technical field [0001] The invention relates to the detection of heat treatment quality of steel, in particular to a method for detecting the amount of residual austenite and the lack of tempering of steel by using the comparison method of Rockwell and Leeb hardness. Background technique [0002] In the past, the lack of tempering of Cr12MoV must be determined by metallographic analysis. In a large number of mold heat treatment production inspections, the quality indicators for acceptance of mold heat treatment are hardness, appearance, deformation, and metallographic structure after tempering. The first three items are relatively intuitive and easy to test. For the inspection of the metallographic structure, it is necessary to take samples from the mold insert, which will generate processing stress on the workpiece and affect the performance of the mold. It is impossible to inspect the metallographic structure of each workpiece in production. Because metallographic inspe...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N33/20G01N3/00
Inventor 唐锐丽甘中明李本言张安民林平尹涛刘凯张显超
Owner DONGFENG MOTOR CO LTD
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